United states department of interior bureau of ocean energy management

Download 9.55 Mb.
Hajmi9.55 Mb.
1   2   3   4   5   6   7   8   9   ...   15

3.1Rufa Red Knot

3.1.1Description of the Species

The rufa red knot (Calidris canutus rufa) is a medium-sized shorebird about 9 to 11 inches (in) (23-28 centimeters (cm)) in length with a proportionately small head, small eyes, short neck, and short legs. It has a black bill which is not much longer than head length. Legs are typically dark gray to black, but sometimes greenish in juveniles or older birds in non-breeding plumage (feathers). Because the proposed project areas are not breeding areas, the red knot would primarily be exhibiting non-breeding plumage which is dusky gray above and whitish below. Many individuals, however, would acquire breeding plumage in the action area, prior to and during spring migration (March-May), and may retain breeding plumage during early portions of fall migration (July-September) (Baker et al. 2013). Juveniles resemble non-breeding adults, but the feathers of the scapulars (shoulders) and wing coverts (small feathers covering base of larger feathers) are edged with white and have narrow, dark subterminal bands, giving the feather a scalloped appearance. Adult body mass varies seasonally, with lowest mean mass during early winter (4.4 ounces (oz) [125 grams (g)]) and highest mean values during spring (7.2 oz [205 g]) and fall (6.1 oz [172 g]) migration.

3.1.2Species Habitat and Distribution

The range of the red knot during migration extends along the Atlantic and Gulf of Mexico coasts of North, Central, and South America, from the Canadian arctic to the southernmost extent of South America.

Breeding occurs within the central Canadian high arctic. Red knots generally nest in dry, slightly elevated tundra locations. Red knots are estimated to begin breeding at two years of age and may survive to seven years. Breeding success of High Arctic shorebirds, like red knot, varies dramatically among years in a somewhat cyclical manner. Breeding seems to be affected by two main factors: weather that affects nesting conditions and food availability, and the abundance of arctic lemmings which affects predation rates.

Southward migration from arctic breeding areas begins in mid-July, stopping at various locations along the Atlantic slope to feed and rest. Red knots would generally be expected to “stopover” within the project area from late July through October, then continue their fall migration to their primary wintering grounds, or remain on the Gulf coast for the winter.

For red knots wintering in South America, the birds are present in the South America wintering areas from November through February. Range and distribution during the fall and spring migration and winter in Mexico and Central America are not well known. It is also unknown if segregation of juvenile and adult red knots occurs on the wintering grounds, if juveniles may winter separately from adults, or occur in habitats not used by adults (78 FR 60024).

During the spring migration, red knots begin moving northward along the Atlantic coast of South America in late February or March. The northward migration is very rapid. Red knots complete their pass along the Atlantic coast of the United States from the middle to the end of May. Known spring stopover areas are along coastal Virginia and Delaware Bay in Delaware and New Jersey, where the birds are present in mid-to late May in high abundance (i.e., approximately 90 percent of the entire population may be present in the Delaware Bay in a single day). After a few weeks during the spring stopover on the mid-Atlantic Coast, the red knot may make additional stops in southern Canada and then return to their breeding grounds in the Canadian Artic. Red knots are also commonly found along the northern GOM coast in Texas and Louisiana during spring migration, roughly during April and into early May.

Wintering areas for the red knot include the Atlantic coasts of Argentina and Chile (particularly the island of Tierra del Fuego that spans both countries), the north coast of Brazil (particularly in the State of Maranhao), the Northwest Gulf of Mexico from the Mexican State of Tamaulipas through Texas (particularly at Laguna Madre) to Louisiana, and the Southeast United States from Florida (particularly the central Gulf coast) to North Carolina (78 FR 60024 and references within). Smaller numbers of red knot winter in the Caribbean, and along the central Gulf coast (Alabama, Mississippi), the mid-Atlantic, and the Northeast United States. In the United States, the red knot is found principally in intertidal marine habitats, especially near coastal inlets, estuaries, and bays, or along restinga formations.

Within the United States, red knot migratory and wintering habitats are principally utilized for resting and foraging activities. In the Southeastern United States, red knots commonly forage on bivalves, gastropods, and crustaceans along sandy beaches, tidal mudflats, salt marshes, and peat banks. In Florida, the birds also use mangrove and brackish lagoons. Along the Texas coast, red knots forage on beaches, oyster reefs, and exposed bay bottoms and roost on high sand flats, reefs, and other sites protected from high tides. Coquina clams are a frequent and often important food resource for red knots, and are common along Gulf beaches and in some places occur abundantly.

These data were summarized by Russell (2014) unless otherwise stated. Purrington (2012) notes the species as an uncommon to common migrant on Gulf beaches and uncommon to scarce winter visitor. The birds seem to disappear in the coldest winters, perhaps moving down the Texas coast or even farther south. Most wintering birds have been documented within the Grand Terre/Grand Isle region west to Raccoon Island, Terrebonne Parish (35 on 6 February 2011), but presumably some may winter offshore on the seldom-visited Chandeleur Island chain. A high count of 70 individuals was documented on 6 February 2011, on Timbalier Island. More “normal” winter counts range from 1 to 10 birds.

Wintering birds appear to be largely absent from the southwestern Louisiana beaches where they are regular during spring and fall migration, even occurring occasionally in rice fields and coastal marshes as far inland as the Intracoastal Waterway and Calcasieu Lake.

Red knot numbers increase in April and early May with a peak count documented in southeast Louisiana of 530 individuals on Grand Isle on 1 May 2004. More recently, the Barataria-Terrebonne National Estuary Program (BTNEP) has been recording presence of red knots on 13 miles (21 km) of shoreline at Caminada Headland during bi-monthly wintering shorebird compliance surveys for piping plover (BTNEP, unpublished data). These surveys recorded an average of 11.7 red knots per survey from highly variable sightings; ranging from 0 individuals on numerous occasions to a high of 64 individuals during a single survey in September of 2013. Spring migration banding efforts by BTNEP and their partners have also documented relatively large flocks (100+ or more) of red knots on Grand Isle annually from 2014 through 2016 (unpublished data). The source of these birds is currently unknown but research is underway to determine the migratory patterns of birds observed in Louisiana. See the project specific chapters for red knot use of the project areas.

3.1.3Status and Cause of Decline

The red knot was proposed as a threatened species on September 30, 2013, due to loss of both breeding and nonbreeding habitat; potential for disruption of natural predator cycles on the breeding grounds; reduced prey availability throughout the nonbreeding range; and increasing frequency and severity of asynchronies (“mismatches”) in the timing of the birds’ annual migratory cycle relative to favorable food and weather conditions. On December 11, 2014, the rufa red knot was listed as a threatened species under the Endangered Species Act of 1973, as amended.

Assessing the population size of a wide-ranging migratory species such as the red knot is difficult as counts within their expansive Arctic breeding areas are not feasible. More recently, analysis of multi-year data generated within two key red knot localities (Tierra del Fuego, wintering area and Delaware Bay, migration stopover area) demonstrated roughly a 75 percent decline in species’ population estimates since the 1980s (78 FR 60024 and references within).

A large portion of individual red knot accounts occurring within the fall or spring stopover and/or wintering areas along the Gulf coast has been documented within a centralized database (AKN 2013). The southeastern wintering population (Florida, Georgia, South Carolina, North Carolina, and Virginia) was reported at approximately 7,500 individuals and 4,500 individuals in 2005 and 2006, respectively. Five surveys along the west coast of Florida between 2005 and 2010 indicated an approximate average of 1,432 individuals. Records compiled prior to 1999 indicated the Louisiana coastline supported approximately 2,500 red knots. Red knots have been observed along other Gulf coast States at various locations, though generally in lower numbers (Alabama = 70, Mississippi = 35) across nearly all months of the year (AKN 2013). Red knots in southwest and northwest Florida have been observed utilizing more than one site within a region or sub-region. In the northwest birds during spring and winter moved among the sites at distances of 5 kilometers (km), 23 km, and 27 km (Smith 2010) and birds in the in southwest during the winter moved among sites varying between 0.6 and 12.4 miles (1-20 km) (Schwarzer 2011).

Main threats to the red knot in the United States include: reduced forage base at the Delaware Bay migration stopover area; decreased habitat availability from beach erosion, sea level rise, and shoreline stabilization in Delaware Bay; reduction in or elimination of forage due to shoreline stabilization, hardening, dredging, beach replenishment, and beach nourishment in Massachusetts, North Carolina, and Florida; and beach raking which diminishes red knot habitat suitability. These and other threats in Canada and South America are detailed in the Species Assessment and Listing Priority Assignment Form (USFWS 2011) and the proposed listing rule (78 FR 60024). Unknown threats may occur on the breeding grounds.

Download 9.55 Mb.

Do'stlaringiz bilan baham:
1   2   3   4   5   6   7   8   9   ...   15

Ma'lumotlar bazasi mualliflik huquqi bilan himoyalangan ©hozir.org 2020
ma'muriyatiga murojaat qiling

    Bosh sahifa
davlat universiteti
ta’lim vazirligi
O’zbekiston respublikasi
maxsus ta’lim
zbekiston respublikasi
o’rta maxsus
davlat pedagogika
axborot texnologiyalari
nomidagi toshkent
pedagogika instituti
texnologiyalari universiteti
navoiy nomidagi
samarqand davlat
guruh talabasi
ta’limi vazirligi
nomidagi samarqand
toshkent axborot
toshkent davlat
haqida tushuncha
Darsning maqsadi
xorazmiy nomidagi
Toshkent davlat
vazirligi toshkent
tashkil etish
Alisher navoiy
Ўзбекистон республикаси
rivojlantirish vazirligi
matematika fakulteti
pedagogika universiteti
таълим вазирлиги
sinflar uchun
Nizomiy nomidagi
tibbiyot akademiyasi
maxsus ta'lim
ta'lim vazirligi
махсус таълим
bilan ishlash
o’rta ta’lim
fanlar fakulteti
Referat mavzu
Navoiy davlat
umumiy o’rta
haqida umumiy
Buxoro davlat
fanining predmeti
fizika matematika
universiteti fizika
malakasini oshirish
kommunikatsiyalarini rivojlantirish
davlat sharqshunoslik
jizzax davlat